The invention relates to a releasable non-return valve. A known releasable non-return valve is described in DE 18 14 214 A 1. A valve of this type serves, for example, for controlling and hydraulically securing the walking support in underground mining. In the closed state the non-return piston serves to secure against the more than 400 bar operating pressure of the hydraulic ram. For drawing the walking support frame the non-return piston can be released hydraulically in order to produce a connection between the operating space at high operating pressure, e.g., the hydraulic ram, and the return line.
Valves of this type, due to their use in underground mining, must, on the one hand, meet very high reliability requirements. On the other hand, when using water as hydraulic fluid, valves of this type are subjected to high load due to the extremely high pressures, the very large amounts of fluid, and the high frequency of shifting. For this reason, the wear-prone parts of these valves are implemented in the form of cartridges. As such a valve cartridge, an essentially cylindrical body is inserted into the valve housing, which is usually a valve block into which several valve holes for several valves are introduced, where in said essentially cylindrical body the valve pistons are guided and the valve seats and valve chambers are formed. In case of wear or after the expiration of the fixed service lifetime, the cartridges with the valve pistons guided therein can then be removed from the valve housing or valve block and replaced.
In the known non-return valve a discharge valve is provided which produces, through the action of the release piston, a throttled connection between the non-return valve's working chamber, which is under very high operating pressure, and the connector chamber connected to the return line before the non-return piston is lifted from its seat and a large flow cross section between the working chamber and the connector chamber is released. Through this discharge valve it is possible, first, to reduce, at least in part, the pressure of the operating space and the working chamber and thereby, when opening the large flow cross section, to avoid high pressure differentials and flow rates. In the known valve, the discharge valve is mounted in the non-return piston so that the discharge valve always has to be mounted and dismounted together with the non-return valve, even though their service lifetimes, due to their different loads, are clearly different.
It is an objective of the invention to extend the known valve in such a manner that the non-return valve and the discharge valve do in fact work together in the desired manner with regard to their function but are independent of one another with regard to their structural implementation and, in particular, can be replaced independently of one another.